Conjunctive Photoluminescence Enhancement Through Plasmonic and Photonic Band-Gap Pathways in a Chiral Self-Assembled System

摘要

We describe two parallel pathways for enhancing the intrinsic photoluminescence of an organic emitter dispersed in a liquid crystal(LC)medium.The pathways have independent origins:(i)Metal enhanced fluorescence(MEF)incorporating gold nanoparticles having an organic shell of pro-mesogenic cholesterol esters;and(ii)Matching the photonic band gap(PBG)due to the helical structure in a self-assembled chiral system with the excitation wavelength.This unprecedented combination of both pathways achieves a level of photoluminescence exceeding the sum of the contribution from the individual methods.This conjunctive protocol results in an overall enhancement by a factor of 37 between the emitter dispersed in a non-chiral LC and that appealing to both MEF and PBG pathways.Circular polarized luminescence measurements also show that this protocol helps in effective discrimination of chiral light achieving a large dissymmetry factor whose magnitude(+0.33)is comparable to the highest recorded to date.Electric field switching between two states is also shown to result in appreciable fluorescence modulation.Being generic in nature the protocol employed can be adapted to a variety of situations with the large magnitude as well the modulation level suitable for applications such as biosensors,various analyte detection,and other photonic devices.